Those who use Fluent 5 for geophysical problems - note that there is an error (relevant only for geophysical problems) which can be corrected by a UDF. namely, the energy equation does NOT contain the gz term (See the forms of the energy equation in the book of Byrd, stewart and Lighthill). I was wondering if anyone in this list has ever tried transforming the variable in the energy equation from temperature to potential temperature. The reason is that in geophysical problems the gradient of heat is proportional to the potential energy gradient, rather than the energy gradient as in Fluent and other packages. Any help on this would be appreciated: anybody knowing of any publications on the subject ?